Continuous casting line having individual roller engagement

ABSTRACT

A continuous casting line, which has a mold for the output of a strand and a strand guide connected to the mold having a plurality of rollers arranged in pairs for transporting the strand in a conveying direction. One or more of the rollers can be engaged so that a thickness reduction of the strand occurs in the strand guide.

TECHNICAL FIELD

The invention relates to a continuous casting installation, which has amold for delivering a strand and a strand guide, adjoining the mold,with rollers arranged in pairs. The invention also relates to a methodfor casting a strand by means of such a device.

BACKGROUND OF THE INVENTION

FIG. 1 schematically shows a known continuous casting installation, thestructure of which is referred to as a “vertical bending machine”, sincethe cast strand is first guided vertically downward by means of a strandguide, then deflected along an arc and transported further horizontally.

The structure and the operating principle of the continuous castinginstallation of FIG. 1 in detail: The liquid metal to be cast is fed toa mold 1, for instance from a pouring ladle that is not shown. The mold1, which may be configured as a funnel mold, brings the molten metalinto the desired slab form. The strand S, which has not yet solidifiedright through, leaves the mold 1 vertically downward and is subsequentlyguided further vertically downward along the strand guide 2, while itprogressively cools down. The strand guide 2 has in the present exampletwo structurally similar curved segments 21 and 22, which form a bendingregion of the strand guide 2. The segments 21 and 22 have rollers 24arranged in pairs, in order to transport the strand S in a conveyingdirection F. The rollers 24 are not connected to a drive, but rather thestrand S is drawn out from the strand guide 2 by a withdrawal andstraightening unit 3, which is located at the end of the bending region.During transport, the strand 1 is cooled, usually by spray water,whereby it gradually solidifies from the outside inward.

The withdrawal and straightening unit 3 may be regarded as part of aconnecting system that is provided between the strand guide 2 and arolling mill 7 for rolling the cast strand S. The connecting system mayalso have a separating device 4 for dividing the strand S into slabs ofa certain length, a furnace 5, to adjust the temperature of the strand Shomogeneously and bring it to a temperature suitable for rolling, and adummy bar rocker 6. If a dummy bar rocker 6 is provided, for startingthe installation a dummy bar can be transported to the furnace 5 anddeposited there.

A continuous casting installation of the type described above isdescribed in DE 10 2015 210 865 A1. DE 10 2015 215 187 A1 also describesa comparable melt-metallurgical installation with a mold and a strandguide.

For low annual production or for other reasons, for instance in the casewhere it is used in a difficult environment or for reasons of cost orwhen producing special alloys, it may be advisable to design theinstallation more compactly and at lower cost with regard to procurementand operation. In order to make the installation of the type describedabove smaller, the two segments 21, 22 may possibly be replaced by asingle segment, which is equipped with pairs of rollers in order totransport and bend the strand leaving the mold before it enters thewithdrawal and straightening unit.

One problem that stands in the way of making the installation smaller isthat the strand cannot be as thin as desired when it leaves the mold.The distance between the immersion pipe and the mold wall must not betoo small, in order that the liquid metal can circulate in the mold. Theimmersion pipe itself must have a minimum diameter in order not tobecome clogged too quickly. Furthermore, the dummy bar that istransported up to the mold from the delivery side for starting theinstallation has a minimum thickness that generally cannot go below 40mm. The fact that, for all these reasons, the strand cannot be cast asthin as desired has the effect that the rolling mill cannot be simplydesigned more compactly, since the rolling mill must be capable ofrolling the slabs cast with a certain minimum thickness to the desiredtarget thickness.

SUMMARY OF THE INVENTION

An object of the invention is to improve a continuous castinginstallation of the type described above, in particular to provide acontinuous casting installation (by analogy a method) which, whileretaining functionality, can be designed particularly compactly and/orcan be operated in an energy-saving manner and/or has a high level ofoperational reliability and casting quality.

The object is achieved by a continuous casting installation with thefeatures of claim 1 and a method with the features of claim 11.Advantageous developments follow from the subclaims, the followingsummary of the invention and the description of preferred exemplaryembodiments.

The continuous casting installation according to the invention servesfor casting a strand in the melt-metallurgical sector, i.e. a strand ofa metal, in particular a metal alloy, preferably steel. The installationis preferably designed as a vertical bending machine, but may also be ofa different form of construction. Thus, the installation may for examplealso be designed as a bow-type installation or vertical slab caster. Thecontinuous casting installation has a mold, which may be configured as afunnel mold. The mold is designed to deliver the strand, preferablyperpendicularly downward when seen in the direction of gravity. For thispurpose, the mold is fed the molten metal to be cast and it is broughtinto the desired form of a strand or slab by the mold, in that the notyet solidified-through strand is discharged out of a correspondinglyshaped outlet opening of the mold. The mold is adjoined by a strandguide, which has a number of rollers arranged in pairs for transportingthe strand in a conveying direction. The rollers arranged in pairsrespectively form a gap and altogether form a gap passageway, throughwhich the strand passes in the conveying direction. According to theinvention, one or more of the rollers of the strand guide are adjustablesuch that a reduction in thickness of the strand takes place in thestrand guide. In other words: the rollers concerned of the strand guideare adjustable such that, during the regular casting process, thethickness of the strand leaving the mold is already reduced in thestrand guide, preferably before it has solidified through completely.

The reduction in thickness of the strand in the strand guide allows arolling mill that may be present, adjoining the strand guide or aconnecting system in the conveying direction, to be designed morecompactly. Typically, such a rolling mill has a number of, for examplefive, rolling stands (passes). Using the reduction in thicknessaccording to the invention in the strand guide allows at least onerolling stand to be omitted. As a result, the installation as a whole,consisting of the continuous casting installation, connecting system androlling mill, can be produced altogether more compactly, and possiblyalso at lower cost. Alternatively, with a conventional design of therolling mill, a greater reduction in thickness of the strand can beachieved. It should be pointed out that less energy is required for thecompressing of the strand that is still liquid in the core than would berequired in the rolling mill if the reduction in thickness in the strandguide were not used. This technical effect leads to an energy saving andto a further cost reduction, both in terms of the operating costs and interms of the procurement costs. A further technical advantage of thereduction in thickness of the strand in the strand guide is that thethickness of the strand does not have to be minimized at the end of themold. It was stated in the section entitled “Background of theinvention” that, for various reasons, the strand cannot be as thin asdesired at the end of the mold. The further the thickness of the strandat the mold approaches this minimum limit, the greater the risk ofbreak-outs or other production defects becomes. The reduction inthickness in the strand guide can consequently lead to an improvement inoperational reliability if the strand thickness at the mold is chosengenerously, without thereby lessening the overall reduction in thicknessat the delivery of the rolling mill. Furthermore, the internal qualityof the strand can be improved, since the afterflow of liquid moltenmetal is reduced by the reduction in thickness in the strand guide.

Preferably, the rollers of the strand guide comprise first pairs ofrollers, which directly adjoin the mold, and pairs of reducing rollers,which directly adjoin the first pairs of rollers in the conveyingdirection, the rollers of the first pairs of rollers beingnon-adjustable, as a result of which no reduction in thickness of thestrand takes place in this region of the strand guide, i.e. a regionthat directly adjoins the mold. According to this preferred embodiment,the reduction in thickness consequently only commences “later”, once thestrand has run through the first pairs of rollers. As a result,fluctuations in the casting level can be prevented, and it is preventedthat the strand becomes detached from the mold wall, whereby theoperational reliability is improved further. A good compromise betweenoperational reliability, compactness and reduction in thickness isachieved if the strand guide has two or three first pairs of rollers andeight to fifteen pairs of reducing rollers.

Preferably, the rollers of the strand guide also comprise last pairs ofrollers, which adjoin the pairs of reducing rollers in the conveyingdirection, are preferably adjustable, but do not lead to any furtherreduction in thickness of the strand. According to this embodiment, nofurther reduction of the strand thickness takes place in the lastportion of the strand guide, for example before the strand is taken upby the rollers of a withdrawal and straightening unit. Preferably, theinstallation is controlled such that, during regular casting, the lowestpoint of the liquid pool of the strand lies in the region of the lastpairs of rollers. The lowest point of the liquid pool refers here to theposition of the strand in the conveying direction at which the stillliquid core goes over into the solidified-through region. Since thestrand solidifies at the surface first and the temperature increasesfrom the outside inward, the liquid core has approximately the form of acone in the conveying direction, with the tip of the cone being referredto as the lowest point of the liquid pool.

If the strand guide is adjoined in the conveying direction by awithdrawal and straightening unit, which has a number of driven rollersand is designed to withdraw the strand actively from the strand guide,the strand is preferably solidified through when it reaches thewithdrawal and straightening unit.

Preferably, the strand guide has a bending region, in which the strandis bent. If the continuous casting installation is constructed as avertical bending machine, the strand leaves the mold verticallydownward, is guided downward by the strand guide and is subsequentlydeflected along an arc. In this case, the strand does not have to bebent completely into the horizontal within the strand guide. Theremaining bending into the horizontal takes place in the withdrawal andstraightening unit. After that, the strand may be further transportedhorizontally, in order to run through further stations, such as forinstance a withdrawal and straightening unit, a separating device fordividing up the strand into slabs of a certain length, a furnace and arolling mill.

Preferably, the strand guide has one or more exchangeable segments, eachwith a number of rollers arranged in pairs. In this way, a conventionalcontinuous casting installation without a reduction in thickness can beretrofitted in an easy way with a strand guide of the type described.Exchanging one or more segments of a conventional strand guide for oneor more segments with adjustable rollers allows the retrofitting to beperformed in a modular manner. Thus, smaller delivery thicknesses fromthe strand guide, and as a result thinner final dimensions at thedelivery of a rolling mill that may be present, can be obtained at asubsequent time by procuring segments with individual roller adjustment.If thinner final dimensions are only to be produced occasionally, it ispossible to work with a number of non-adjustable segments and only toinstall an adjustable segment (by analogy a number of adjustablesegments) in the case of production of the particularly thin dimensions.Alternatively, the adjustable segment (by analogy a number of adjustablesegments) may be permanently installed, the adjustable rollers onlybeing moved into a reducing position in the case of the production ofthe particularly thin dimensions and otherwise being in an inactiveposition without a reduction in thickness.

Preferably, the adjustable rollers are hydraulically, magnetically orelectromotively actuable. According to a particularly preferredembodiment, the strand guide has one or more hydraulic cylinders, ineach of which a piston is hydraulically displaceable for adjusting anadjustable roller attached thereto. By hydraulic activation, forinstance by means of oil, the piston can be moved back and forth betweenthe inactive position and the reducing position. Both rollers of a pairof rollers or else only one roller of the pair may be adjustablyprovided. Moreover, in certain variants of the embodiment it may beadvisable that adjustable rollers can be brought into more than twopositions, in particular are adjustable in a stepless manner. Thus,according to a variable exemplary embodiment, the thickness of thestrand can be reduced to different delivery thicknesses. Alternativelyor in addition, a frame part of the aforementioned segment (by analogy anumber of segments) of the strand guide may also be adjustably designed,whereby a number of rollers are adjustable in groups for reducing thestrand thickness.

The method according to the invention concerns the casting of a strandby means of a device of the type described above, one or more rollers ofthe strand guide being adjusted such that, during the regular castingprocess, the thickness of the strand is reduced in the strand guide. Thetechnical effects, preferred embodiments and contributions to the priorart that have been described with respect to the device applyanalogously to the method.

The adjustment profile of the rollers can be suitably establishedaccording to the degree of reduction, distance over which the reductiontakes place, material of the strand, etc. Thus, the reducing positionsof the rollers may for instance be distributed linearly orparabolically, so that the reduction in thickness takes place linearlyor parabolically along the strand guide.

According to a particularly preferred embodiment, the reduction inthickness of the strand takes place with the core not solidifiedthrough, which makes energy-saving operation of the installationpossible and also contributes to an improvement of the casting quality.

Preferably, the adjustable rollers are adjusted with process parameterstaken into account and on the basis of a temperature calculation model,with which temperature properties of the strand, for instance theposition of the lowest point of the liquid pool and/or the strand shellthickness, can be determined.

Further advantages and features of the present invention can be derivedfrom the following description of preferred exemplary embodiments. Thefeatures described therein can be implemented individually or incombination with one or more of the features set forth above, in as faras the features are not mutually exclusive. The following description ofthe preferred exemplary embodiments is performed with reference to theappended drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically shows a continuous casting installation, designedas a “vertical bending machine”, with two strand guiding segments and awithdrawal and straightening unit for transporting the cast strand.

FIG. 2 schematically shows a continuous casting installation withadjustable rollers.

FIGS. 3a and 3b show hydraulic activation of adjustable rollers.

Detailed description of preferred exemplary embodiments

Preferred exemplary embodiments are described below on the basis of thefigures. Elements that are the same, similar or act in the same way areprovided with identical reference signs, dispensing to some extent withrepeated description of these elements so as to avoid redundancies.

FIG. 2 schematically shows a continuous casting installation, the basicconstruction of which is similar to FIG. 1. The mold 1 is adjoined bythe strand guide 2. At the outlet of the strand guide 2, the withdrawaland straightening unit 3 is provided, for withdrawing the strand S fromthe strand guide 2.

As a difference from the installation of FIG. 1, the strand guide 2 ofthe exemplary embodiment of FIG. 2 has only a single segment 23, even ifaccording to other exemplary embodiments a number of segments may beprovided. A continuous casting installation with only one segment 23 hasa greater rigidity and can absorb the bending forces produced by thewithdrawal and straightening unit 3 better than a continuous castinginstallation of the same length with a number of segments. In the caseof a continuous casting installation with two or more segments, after afault, such as for instance a break-out, it may possibly be necessaryfor all of the segments to be changed one after the other. The timestaken to perform these changes are generally much shorter in the case ofa continuous casting installation of which the strand guide 2 has only asingle segment 23, since the entire strand guide 2 can be changedwithout segments having to be connected to one another. When connectingsegments to one another, there is the risk that two adjacent segmentsare not connected exactly to one another. Contaminants, wear and/orincorrect alignment of the segments may lead to stresses in the strandS, which leads to an increased risk of cracking. These sources ofdefects can be reduced by a strand guide 2 with a single segment 23, forwhich reason this exemplary embodiment is preferred—in particular withregard to a compact and low-cost installation.

The segment 23 has a number of rollers 24 a, 24 b, 24 c (referred tojointly as rollers 24), which are arranged in pairs, whereby they (tworollers 24 are always facing one another) form a gap passageway, throughwhich the strand S leaving the mold 1 downward passes along a curvedpath and is guided. The not yet solidified-through strand is accordinglyfirst guided vertically downward, then deflected by the strand guide 2along an arc and after that transported horizontally. During transport,a cooling of the strand S takes place, which may possibly be activelyassisted and/or controlled by applying a cooling fluid.

The withdrawal and straightening unit 3 is arranged as part of aconnecting system downstream of the segment 23 in the conveyingdirection F, in order to withdraw the strand S from the strand guide 2and bend it completely into the horizontal. For this purpose, thewithdrawal and straightening unit 3 has a number of rollers 31 arrangedin pairs, which are driven rollers, for instance driven by one or moreelectric motors (not represented).

Even if other components have not been shown in FIG. 2 for the sake ofoverall clarity, the continuous casting installation of the presentexemplary embodiment may have, as in FIG. 1, a separating device, afurnace, a dummy bar rocker, a rolling mill and/or further components.

As a difference from the continuous casting installation of FIG. 1,according to the present exemplary embodiment one or more rollers 24 ofthe strand guide 23 are adjustable, comprising in particular anadjustability during the casting operation. The adjustability isprovided in such a way that one or more pairs of rollers can be movedtogether, whereby the transporting gap can be varied, in particularreduced, along the conveying direction F.

To distinguish between different groups of rollers of the strand guide2, one or more pairs of rollers directly underneath the mold 1 arereferred to as first pairs of rollers 24 a. Pairs of rollers that followin the conveying direction F are referred to as middle pairs of rollersor pairs of reducing rollers 24 b. The remaining pairs of rollers of thestrand guide 2, which lie directly before the withdrawal andstraightening unit 3, are referred to as the last pair of rollers 24 c.Since the rollers 24 of the strand guide 2 are generally arranged inpairs, the reference signs 24 a, 24 b, 24 c are also used to refer tothe rollers themselves of the pair concerned.

According to a particularly preferred exemplary embodiment, the firstrollers 24 a are non-adjustable, this first group of rollers preferablyhaving two or three pairs of rollers 24 a. The fact that the first pairsof rollers 24 a are non-adjustable, i.e. are mounted in a fixed manner,means that fluctuations in the casting level can be prevented, and it isprevented that the strand S becomes detached from the mold wall.

The middle pairs of rollers 24 b, for example 8 to 15 pairs of rollers,preferably 11 pairs of rollers, are adjustable individually or else ingroups. In particular, they can be moved together, whereby the thicknessof the strand S not yet solidified in the core is reduced in the strandguide 2. Starting for example from a thickness of 52 to 45 mm at themold outlet, the thickness is reduced for instance to 32 to 35 mm,preferably to 20 mm, at the delivery of the strand guide 2.

The last pairs of rollers 24 c, preferably for instance four pairs ofrollers, are preferably also adjustable. However, this adjustment servesonly for following the previously set strand thickness. In this case, nofurther reduction in thickness of the strand S takes place in theportion comprising the last pairs of rollers 24 c.

By varying the casting speed and/or cooling rate, for instance theamount of spray water, the position of solidification right through(lowest point of the liquid pool) in the roller way is regulated, inparticular is arranged such that complete solidification right throughis not within the region of the middle pairs of rollers 24 b. Areduction in thickness of the solidified-through strand would requiremuch greater adjusting forces, whereby the risk of cracking would beincreased.

The adjustment profile of the middle rollers 24 b can be suitablyestablished according to the degree of reduction, distance over whichthe reduction takes place, material of the strand S, etc. Thus, thereducing positions of the rollers 24 b may for instance be distributedlinearly or parabolically. If for example a strand with a thickness of50 mm at the mold outlet is to be reduced to 34 mm in a linear way, with11 reducing rollers 24 b the reduction at each of the reducing rollers24 b is then 16 mm/11=1.4545 mm. At the first rollers of the middlerollers 24 b, the reductions may also be slightly greater, and decreaseparabolically or in some other way, so that at the last reducing roller24 b only a reduction of the strand thickness of approximately 1 mmtakes place.

According to a constructionally simple, low-cost exemplary embodiment,represented in FIGS. 3a and 3b , the middle rollers 24 b (possibly alsothe last rollers 24 c) are movable into precisely two positions byhydraulic cylinders. In this case, in one position, the inactiveposition (FIG. 3a ), no reduction in thickness takes place, while thethickness of the strand S at the corresponding pair of rollers 24 b inthe second position, the reducing position (FIG. 3b ), is reduced.

In the exemplary embodiment of FIGS. 3a and 3b , a piston 25, on which aroller 24 b or 24 c is attached, is provided displaceably in a cylinder26. By hydraulic activation, for instance by means of oil, the piston 25can be moved back and forth between the inactive position and thereducing position. Both rollers of a pair of rollers 24 b or else onlyone roller 24 b of the pair may be adjustably designed. Preferably, onlythe rollers 24 b, 24 c on the loose side are adjustable. Furthermore,the adjustment of the rollers 24 b, 24 c may also be technicallyrealized in some other way, for instance magnetically orelectromotively. Moreover, in certain variants of the embodiment it maybe advisable that one or more or all of the middle rollers 24 b and/orlast rollers 24 c can be brought into more than two positions, inparticular are adjustable in a stepless manner. Thus, according to avariable exemplary embodiment, the thickness of the strand can bereduced to different delivery thicknesses. Alternatively or in addition,a part of the segment frame, preferably the upper frame, may also beadjustably designed, whereby a number of rollers 24 b, 24 c areadjustable in groups for reducing the strand thickness. It is also thecase here that preferably no reduction in thickness takes place at thefirst rollers 24 a and last rollers 24 c. According to a furtherexemplary embodiment, two rollers or pairs of rollers 24 a, 24 b, 24 cmay also be respectively combined in a cassette; these rollers can thenpossibly be adjusted individually or together.

The reduction in thickness described above in the strand guide 2 allowsthe rolling mill 7 to be designed more compactly. Typically, the rollingmill has a number of, for example five, rolling stands (passes). In thiscase it is possible for at least one rolling stand to be omitted. As aresult, the installation as a whole can be produced altogether morecompactly, and possibly also at lower cost. Alternatively, with aconventional design of the rolling mill 7, a greater reduction inthickness of the strand S can be achieved. It should be pointed out thatless energy is required for the compressing of the strand S that isstill liquid in the core than would be required in the rolling mill ifthe reduction in thickness in the strand guide 2 were not used. Thistechnical effect leads to an energy saving and to a further costreduction, both in terms of the operating costs and in terms of theprocurement costs. A further technical advantage of the reduction inthickness of the strand S in the strand guide 2 is that the thickness ofthe strand does not have to be minimized at the end of the mold. It hasalready been explained that, for various reasons, the strand cannot beas thin as desired at the end of the mold. Depending on the material andthe process parameters, this limit typically lies at approximately 45mm. The further the thickness of the strand at the mold approaches thislimit, the greater the risk of break-outs becomes. The reduction inthickness in the strand guide 2 can consequently lead to an improvementin production reliability if the strand thickness at the mold is chosengreater, without thereby lessening the overall reduction in thickness atthe delivery of the rolling mill 7. Furthermore, the internal quality ofthe strand can be improved, since the afterflow of liquid molten metalis reduced by the reduction in thickness in the strand guide 2, wherebyundesired segregations are reduced.

A conventional continuous casting installation without a reduction inthickness in the strand guide 2 can be retrofitted with adjustablerollers 24 b, 24 c. Exchanging one or more segments of a conventionalstrand guide for one segment 23 that contains the adjustable rollers 24b, 24 c allows the retrofitting to be performed in a modular manner.Thus, smaller delivery thicknesses from the strand guide 2, and as aresult thinner final dimensions at the delivery of the hot rolling mill7, can be obtained at a subsequent time by procuring segments withindividual roller adjustment. If thinner final dimensions are only to beproduced occasionally, it is possible to work with a number ofnon-adjustable segments 21, 22 and only to install the adjustablesegment 23 (by analogy a number of adjustable segments) in the case ofproduction of the particularly thin dimensions. Alternatively, theadjustable segment 23 (by analogy a number of adjustable segments) maybe permanently installed, the adjustable rollers 24 b, 24 c only beingmoved into the reducing position in the case of the production of theparticularly thin dimensions and otherwise being in the inactiveposition.

A method for reducing the thickness of the strand in the strand guide 2according to an exemplary embodiment is described below:

The continuous casting installation is started in a conventional waywith the aid of a dummy bar. As soon as the dummy bar is uncoupled andpossibly stowed away by the dummy bar rocker 6, the thickness of thestrand can be reduced. If the bar head (for example of 52 to 45 mm) istoo thick for the rolling mill 7, the non-reduced bar head (for exampleof 4 m in length, which corresponds to the length of the castingmachine, i.e. the distance between the mold 1 and the delivery of thestrand guide 2) can be broken down into scrap in the separating device4. The adjustable reducing rollers 24 b of the strand guide 2subsequently reduce the strand S not yet solidified through in the core.If required, the position of the lowest point of the liquid pool and thestrand shell thickness at all of the positions of the rollers may becalculated by a temperature calculation model. The lowest point of theliquid pool refers here to the position of the strand S in thetransporting direction at which the still liquid core goes over into thesolidified-through region. Since the strand S solidifies at the surfacefirst and the temperature increases from the outside inward, the liquidcore has approximately the form of a cone in the conveying direction,with the tip of the cone being referred to as the lowest point of theliquid pool. The casting speed and cooling rate, preferably the amountof spray water, are then regulated such that the lowest point of theliquid pool is displaced forward into the region of the last pairs ofrollers 24 c. There, the thickness of the strand is not reduced anyfurther. If the already solidified-through strand S were compressed, theadjusting forces required would increase greatly and there would be therisk of internal cracks. The average temperature at the entrance of thefurnace 5 is all the greater the closer the lowest point of the liquidpool gets to the end of the casting machine, i.e. to the delivery of thestrand guide 2. When the withdrawal and straightening unit 3 is reached,the strand S is preferably completely solidified through.

The fact that the continuous casting installation is regulated such thatthe lowest point of the liquid pool is in the region of the last rollers24 c means that an optimum reduction in thickness can be achieved in thestrand guide 2, since all of the reducing rollers 24 b are active, whichwould not be the case with a strand S that has solidified through tooearly.

Variable activation of the reducing rollers 24 b allows different strandthicknesses to be cast, and the distribution of the reduction can beadapted to the process values at the particular time. This is usefulsince the distribution of the reduction is preferably chosen such thatgreater reductions take place in the region with a still completelyliquid core (Liquid Core Reduction “LCR”) than in the region with thefirst dendritic growth in the core (soft reduction). In this way, therisk of internal cracks can be reduced. Since the positions of theliquid boundary and the lowest point of the liquid pool changedynamically with the process values (casting speed, analysis,overheating, casting level, amounts of water, water temperature, etc.),a dynamic temperature calculation model is preferably used for thecalculation thereof. With the reduction in the strand guide 2, the lastreduction is preferably not so far away from the mold 1 that there canno longer be any afterflow of molten metal.

To the extent that they are applicable, all of the individual featuresthat are represented in the exemplary embodiments can be combined withone another and/or exchanged with one another without departing from thescope of the invention.

LIST OF REFERENCE SIGNS

1 Mold

2 Strand guide

3 Withdrawal and straightening unit

4 Separating device

5 Furnace

6 Dummy bar rocker

7 Rolling mill

21,22,23 Segments of the strand guide

Rollers of the strand guide

24 a First rollers/pairs of rollers

24 b Reducing rollers/pairs of reducing rollers

24 c Last rollers/pairs of rollers

25 Piston

26 Hydraulic cylinder

31 Rollers of the withdrawal and straightening unit

S Strand/slab

F Conveying direction

1-13. (canceled)
 14. A continuous casting installation, comprising: amold for delivering a strand; and a strand guide adjoining the mold, thestrand guide having a number of rollers arranged in pairs fortransporting the strand in a conveying direction, wherein at least oneof the rollers is adjustable so that a reduction in thickness of thestrand takes place in the strand guide, wherein the strand guideincludes at least one exchangeable segment having a number of adjustablerollers arranged in pairs.
 15. The continuous casting installationaccording to claim 14, wherein the rollers include first pairs ofrollers that directly adjoin the mold, and pairs of reducing rollersthat directly adjoin the first pairs of rollers in the conveyingdirection, the rollers of the first pairs of rollers beingnon-adjustable so that no reduction in thickness of the strand takesplace in this region of the strand guide, at least one of the rollers ofthe pairs of reducing rollers being adjustable so that a reduction inthickness of the strand takes place in this region of the strand guide.16. The continuous casting installation according to claim 15, whereinall of the rollers of the pairs of reducing rollers are adjustable. 17.The continuous casting installation according to claim 15, wherein thestrand guide has two or three of the first pairs of rollers.
 18. Thecontinuous casting installation according to claim 17, wherein thestrand guide has eight to fifteen of the pairs of reducing rollers. 19.The continuous casting installation according claim to 15, wherein therollers also comprise last pairs of rollers that adjoin the pairs ofreducing rollers in the conveying direction, are preferably adjustable,but do not lead to any further reduction in thickness of the strand. 20.The continuous casting installation according to claim 19, wherein thelast pairs of rollers are adjustable.
 21. The continuous castinginstallation according to claim 19, wherein the casting installation isconfigured so that during a regular casting process a lowest point of aliquid pool of the strand lies in a region of the last pairs of rollers.22. The continuous casting installation according to claim 14, whereinthe strand guide has a bending region in which the strand is bent.{00409382 } 6
 23. The continuous casting installation according to claim22, wherein the continuous casting installation is constructed as avertical bending machine, in which the strand leaves the mold verticallydownward, is guided downward by the strand guide and is subsequently atleast partially deflected along an arc in a direction of horizontal andtransported further.
 24. The continuous casting installation accordingto claim 14, further comprising a withdrawal and straightening unit thatadjoins the strand guide in the conveying direction, the withdrawal andstraightening unit having a number of driven rollers and beingconfigured to withdraw the strand from the strand guide and bend thestrand completely into a horizontal orientation.
 25. The continuouscasting installation according to claim 14, wherein the adjustablerollers are hydraulically, magnetically or electromotively actuable. 26.The continuous casting installation according to claim 25, wherein thestrand guide has at least one hydraulic cylinder in which a piston ishydraulically displaceable for adjusting the adjustable rollers.
 27. Thecontinuous casting installation according to claim 14, wherein theadjustable rollers are adjustable into precisely two positions, the twopositions being an inactive position, in which no reduction in thicknessof the strand takes place at the position concerned in the strand guide,and a reducing position, in which a reduction in thickness of the strandtakes place at the position concerned in the strand guide.
 28. A methodfor casting a strand with a device according to claim 14, comprising thesteps of adjusting at least one of the rollers of the strand guide sothat during casting a thickness of the strand is reduced in the strandguide.
 29. The method according to claim 28, including reducing thethickness of the strand in the strand guide with the core of the strandnot completely solidified.
 30. The method according to claim 28,including adjusting the adjustable rollers taking process parametersinto account and based on a temperature calculation model, with whichtemperature properties of the strand are determined.
 31. The methodaccording to claim 30, including determining a position of a lowestpoint of a liquid pool and/or a strand shell thickness.